It depends ... say you've got a nice project going on, still in infancy, and you post its link on sites like reddit and HN to get feedback. 2000 visitors instantly hit the link and your site crashes exactly when you need it more to stay alive.
Premature optimization is the root of all evil and all that, but going at the other extreme is equally not the smartest thing you can do.
An application like 37signals Basecamp can grow organically over time as the application is maturing and more and more users discover it and start paying for it. But if your project's success depends on the number of users you have (e.g. a social app), it makes sense to think about scaling and reliability a little beforehand.
Remember Twitter? It's still a mystery to me how this app survived having so many outages. Maybe they where lucky, maybe the social aspects where worth it for its users, but that doesn't mean your application will survive if facing such problems.
Premature optimization is the root of all evil and all that, but going at the other extreme is equally not the smartest thing you can do.
An application like 37signals Basecamp can grow organically over time as the application is maturing and more and more users discover it and start paying for it. But if your project's success depends on the number of users you have (e.g. a social app), it makes sense to think about scaling and reliability a little beforehand.
Remember Twitter? It's still a mystery to me how this app survived having so many outages. Maybe they where lucky, maybe the social aspects where worth it for its users, but that doesn't mean your application will survive if facing such problems.